1. Field of the Invention
The present invention relates to a printed circuit board and a method of mounting a terminal board thereon, and more particularly to an improvement in the positional arrangement of mounting pads on the printed circuit board.
2. Description of the Related Art
FIG. 1 illustrates a conventional printed board 1 which is fabricated for obtaining an integrated circuit card, where only a part of the circuit structure is shown. The printed circuit board 1 has an insulating plate 2 on which printed wiring 4 is provided. Regions 3 for accepting integrated circuit devices and discrete electronic elements are defined on the insulating plate 2. On the connector portion 5 of the printed circuit board 1, an exposed linear array of mounting pads 6 is formed along an edge 7 of the printed circuit board 1. The mounting pads 6 are made of a metal or an alloy and are electrically connected to the printed wiring 4.
FIG. 2A illustrates the bottom surface 10B of a terminal board 10 which is to be mounted on the printed circuit board 1, while FIG. 2B illustrates the top surface 10T of the terminal board 10. A linear array of mounting pads 11 is provided on the bottom surface 10B along an edge 13 of the board 10, and the mounting pads 11 are electrically connected to corresponding terminal pads 12 formed on the top surface 10F of the board 10.
FIG. 3 is a perspective view showing a process of mounting the terminal board 10 on the printed circuit board 1. As illustrated in detail in FIG. 4, a solder pattern layer 14 is formed on the mounting pads 6 by means of a solder printing device, and then the terminal board 10 is placed on the printed circuit board 1 (FIG. 3) so that the solder pattern layer 14 is sandwiched between the mounting pads 6 and 11, the mounting pads 11 not being shown in FIG. 3. The overlapped region of the printed circuit board 1 and the terminal board 10 is heated to melt the solder pattern layer 14. The overlapped region is then cooled, so that the terminal board 10 is fixed to the printed circuit board 1, and the mounting pads 6 and 11 are electrically connected to each other.
A module 20 thus obtained is packaged together with a battery, whereby an integrated circuit card (IC card) is obtained. Electronic communication between the IC card and and IC card reader (not shown) is attained by inserting the IC card into the IC card reader, so that the terminal pads 12 are electrically in contact with terminal electrodes provided in the IC card reader. The terminal board 10 is effective in electrically connecting the printed circuit board 1 to the terminal electrodes of the IC card reader because the terminal electrodes of the IC card reader are located at a position which is somewhat higher than the mounting pads 6 of the printed circuit board 1 when the IC card is inserted into the IC card reader.
In the above-described mounting process, the solder material of the solder pattern layer 14 spreads from the mounting pads 6 over the peripheral areas thereof, because the solder material is melted and pushed between the printed circuit board 1 and the terminal board 10. Accordingly, if the respective array pitches of the mounting pads 6 and 11 are relatively small, the solder material spreading from one pad often reaches a neighbouring pad, so that these mounting pads are electrically shorted.